Pipes and adapters of this type are well known and are described in particular in Patent Application Nos. CH 676 081 and EP 745 358 by the same Applicant, the back end of the supply pipe being connected to a supply and control unit that can deliver, via the pipe, various fluids and various currents or electrical signals for actuating and/or controlling various apparatus or instruments able to be connected as required to the front end of the pipe. For this purpose, the front end is provided with a universal coupling that is also called an “attachment”. The latter generally contains several fluid connectors and several electrical connectors. Depending upon the type and nature of the instrument that has to be coupled, all of the connectors of the coupling or only certain of them will be used and will thus be coupled to corresponding connectors of the instrument or of an intermediate coupling, as is explained particularly in EP Patent Application No. 745 358. This is why the coupling or attachment is termed universal. Similar couplings, having a different arrangement of the connectors are disclosed in U.S. Pat. No. 4,080,737.
FIG. 2 of CH Patent No. 676 081 shows the front face of the universal coupling or attachment 400, which is fitted to the front end of the supply pipe. FIG. 1 of this paper corresponds to FIG. 2 of CH Patent No. 676 081, Coupling 400 comprises a body 500 made of insulating material carrying a rotating threaded sleeve 100 that enables coupling 400 to be fixed to the associated couplings in a removable manner. Body 500 contains four connectors 600, 700, 800 and 900 for fluids and four electric connectors 200, 210, 220 and 230, which are arranged in a standarized manner so that they can be used with instruments from different manufacturers. In the example described here, which refers to the products marketed under the name 4VLM by Bien-Air Dental SA, Bienne, Switzerland, connector 600 is associated with a conduit which brings pressurized air to the turbine of a handpiece, whereas connector 700 is associated with a return conduit for the air. Connector 800 is associated with a conduit which brings water to the instrument, whereas connector 900 is associated with a conduit that supplies pulsed air to the instrument, wherein the water and pulsed air are for cleaning, drying or cooling the work area. The pair of electric connectors 200 and 210 is for an electric circuit powering a lamp for illuminating the work area. The pair of electrical connectors 220 and 230 is used for the circuit powering an electric motor for a handpiece or for an electric device of a different type from a motor or a lamp, for example, an ultrasound scaling apparatus. Using the supply circuit passing through connectors 220 and 230 is also known for transmitting electric control or measurement signals, in the form of encoded pulses.
The front face arrangement shown in FIG. 2 of CH Patent No. 676 081 has been very widely used in the world for many years, particularly because of its versatility and the standardization of the couplings supplied by the main manufacturers. However, this standardization has a drawback in certain cases, because it becomes almost impossible to install additional connectors in such a coupling, since virtually all of the available places on the front face are occupied by the usual connectors. With developments in technology and in particular in dental or surgical handpiece, additional or different connections between the hand piece and the control and supply unit have become desirable or necessary, and it would be useful to make them without having to alter most of the couplings of the instruments that practitioners are currently using. A typical example of such an additional connection is the earthing (grounding) of certain apparatus or instruments whose electric circuits could pose a risk for a patient. Earthing, which is compulsory in certain cases, would mean using one of the four connectors 200 to 230 in the example of FIG. 1 (FIG. 2 of CH Patent No. 676 081), and could thus lead to removal of one of the electric circuits. There, therefore, exists a requirement for another solution to this problem.
In other technical fields, conductive circuits have been incorporated in fluid pipes and in their connectors in order to form an earth line. For example, in order to dissipate any electrostatic charges, a solution shown in FIGS. 6 to 8 of EP Patent Application No. 1 310 721 uses pipes having a conductive layer and connectors having contact parts located inside the fluid conduit.
Another example is found in U.S. Pat. No. 1,890,290, which discloses couplings for fire hose pipes whose walls contain a pair of conductive wires forming an electric signal transmission circuit. The connection of one of the wires is carried out directly by the threaded metal rings of the couplings, whereas the connection of the second wire is carried out via contact parts arranged in the fluid conduit. This arrangement appears to be difficult to use reliably, if one considers that at least one of the two electric lines would have to be well insulated over its entire length with respect to the external medium and the water contained in the pipe.